1. Field of the Invention
The present invention relates to air driven power generators, particularly to power generation, size, weight, and efficiency improvements of ram-air driven turbines and the like. An aerodynamic low-pressure exhaust ducting mounted on the discharge side of an air-driven turbine has been developed. The invention generates an increased ratio of total-to-static pressure across a Ram Air Turbine (RAT) developed for a combined Ram air Power and Cooling unit (RPC), resulting in increased turbine power generation when compared to a conventional RAT. Improvements in the ram-air turbine design and the functionality of the turbine exhaust ducting provide increased power extraction capability resulting in a smaller and lighter power generator that minimizes the overall system size and weight.
2. Description of the Related Art
A RAT is a turbine driven by free-stream air that flows past an aircraft during flight. RATs can be used to develop mechanical power that can be directly converted into electrical power using a generator, or both. The mechanical shaft power can be used to power any mechanical device, including but not limited to hydraulic systems, vapor-compression cooling system compressors, circulation pumps, or refueling pumps. Electrical power can be used for electronic subsystems, such as onboard avionics equipment, electronic warfare equipment, and auxiliary backup power systems. RATs can be mounted directly onboard an aircraft fuselage or on secondary wing mounted pods or stores. At wing-mounted locations, the RAT can be located either at an external location where the turbine is directly exposed to free-stream air, or an internal location inside a pod, where the free-stream air is ducted to the turbine through an inlet that is exposed to free-stream air. Prior work on internal RAT's have utilized ducts to deliver free-stream air to the turbine. By locating the RAT internally, however, pressure losses occur in the inlet ducting, which decreases turbine output power. Such internal RAT arrangements are also limited to ambient static pressure on the turbine discharge. The present invention makes it more feasible to locate a RAT in an interior location and extract additional power relative to a conventional RAT.
U.S. Pat. No. 3,463,402 (Langston), teaches the use of an ejecting exhaust nozzle to generate turbulence between two streams of gas, thus suppressing the noise normally generated from shear stresses at the interface of the higher velocity core gas stream with the lower velocity gas stream in a gas turbine engine. U.S. Pat. No. 3,409,228 (Mehr) teaches an ejector nozzle for cooling a gas turbine engine and exhaust nozzle, whereby an ejector is in flow communication with an engine inlet and its purpose is to draw additional ram airflow through a bypass duct to provide cooling to the engine and exhaust nozzle. U.S. Pat. No. 5,435,127 (Luffy) also teaches the use of an ejector nozzle to provide cooling airflow to components of a gas turbine engine; however, this system requires an additional boost pump. None of the prior art teaches the use of a converging/diverging ram air ejector nozzles to increase the total-to-static pressure ratio across a ram air driven turbine for the purpose of increasing power.
The mechanical power that can be developed from a RAT is a function of the total-to-static pressure ratio across the turbine rotor. The pressure at the face of the turbine rotor is a function of the aircraft velocity, altitude, and environmental conditions and is specified as the total pressure or the maximum obtainable pressure that can be utilized for power generation. If a method to decrease the static pressure is not utilized, the power generating capability of the RAT is limited to the total pressure developed by the aircraft and the ambient static pressure.G